Particle separating apparatus



Jan. 26, 1965 A. H. PITcHFoRD 3,167,503

PARTICLE SEPARATING APPARATUS Filed April 28, 1961 2 Sheets-Sheet l Jan. 26, 1965 A. H. PlTcHFoRD PARTICLE SEFARATING APPARATUS 2 Sheets-Sheet 2 Filed April 28, 1961 HIGH PRESSURE 44 SOUZCL INVENTOR. @Erf/UPM Pfr-cameo, W7/27 United States Patent 3,167,5tl3 PARTICLE SEPARATING APPARATUS Arthur H. litchford, 501 Castle Shannon Pittsburgh, Pa.

Filed Apr. Z8, 1962i, Ser. No. 196,325 7 Claims. (Cl. 299-242) This invention relates to apparatus for segregating particles according to size, and more particularly to apparatus of the type described which is both etlicient and rapid in operation.

As is known, particles are commonly separated into different size ranges by a conventional screening process wherein particles of random sizes are brought into contact with a screen of a predetermined mesh size, and the screen and/or particles mechanically agitated to eventually bring all particles into contact with the screen such that those particles at or below the screen mesh size will pass through the screen while those of larger size will not pass through. Existing screening methods of this type, although used extensively, are relatively slow, particularly when it is desired to separate a batch of particles into many'edilerentrsize ranges, which requires a plurality or. successive screeningstepswith screens of different sizes. In addition, in the case of line'particles (i.e., powdered materials), the screen tends to blind or clog and'prevents further particles from passing therethrough, the reason being, among other things, that static charges build up in the particles and/or screen which cause the particles to cling to the screen.

As an overall object, the present invention seeks to provide a technique for rapidly segregating particles into diiferent size ranges.

Another object of the invention is to provide apparatus of the type described capable of segregating powdered materials into different size ranges while avoiding the problem of blinding or clogging of screens which is present in conventional particle separating techniques.

Still another object of the invention is to provide apparatus for particle size segregation adapted to continuously and automatically separate particles into dilferent size ranges.

In accordance with one feature of the invention, there is provided a particle receiving chamber, spaced particle separating means in the chamber adapted to permit the passage of particles of a predetermined size, means in the chamber for carrying particles to and away from one and then the other of said spaced separating means, collecting means for receiving particles passing through the particle separating means, and means for discharging the particles of a size too large to pass through the particle separating means out of the chamber after a time has elapsed suihcient to permit all particles of said predetermined size to pass to the collecting means. Preferably, the spaced particle separating means are screens arranged at opposite ends or sides of the chamber. The means for carrying particles to and away from the spaced separating means is a fluid, preferably air, pulsed alternately into the particle receiving chamber through one screen and out through the other. In the pulsing cycle, air goes in through the screen at one end of the chamber, cleaning this screen on the way in; continues through the chamber and blasts the particles against the screen at the opposite end of the chamber; nally passing on to a collector. When particles are blown against a line screen in this manner, even though the individual particles be the same or smaller than the screen size, the screen will blind or clog very rapidly and prevent any further material from passing therethrough. Consequently, in the present invention the air is alternately pulsed from one end of the particle receiving chamber to the other; and on the second ice pulse in the cycle, the air flow is reversed, thereby blast.

ing particles against the previously cleaned screen while cleaning the screen against which particles were blasted by the previous pulse. ln this manner a clean screen is always presented against which particles are blasted. The collecting means may be a filter paper bag, a settlement chamber, a cyclone type centrifugal collector, an electrostatic precipitatcr, a screen or the like means for removing the sized particles from the fluid carrier passing through the spaced screens. ln order to remove particles which are of a size too large to pass through the screens, a valve is provided in the chamber, and this valve opened after particles of a size to pass through the screens have been removed from the chamber, the remaining particles being blasted through the valve by introducing fluid under relatively high pressure into the chamber. In certain cases, it may be desirable to employ a check valve for this purpose. During the time when the particles are alternately carried to and away from the spaced screens to separate the smaller particles from those of larger size, the check valve will remain closed. After all of the small particles are separated, however, fluid under higher pressure is introduced into the chamber to open the check valve and blow out all of the larger-sized particles to prepare the chamber for a successive batch of particles to be separated.

Y `VlnY accordance with another aspect of the invention, a plurality of particlerrxeceiving chambers of the type described above may be connectedrinseries with each chamber discharging through its valve intothenext succeeding chamber. By providing screens of larger mesh size in succeeding chambers, the output from each chamber to itc associated collecting means will be particles of progressively increasing size. Thus, a batch of particles of random sizes may be separated into smaller batches of discrete size ranges, and this achieved rapidly and eiliciently due to the alternate cleaning of the spaced screens in each chamber.

In accordance with still another aspect of the invention, the foregoing procedure may be effected on a continuous production basis with particles being fed into the rst chamber from a storage bin, and air blasted into each chamber in succession, starting from the last seriallyconnected chamber and progressing to the rst, whereby the particles of each chamber which do not pass through the spaced screens for that chamber may be automatically, or semi-automatically, transferred to the next chamber through appropriate valve means where particles of a particular size range will be separated from those of larger size.

The above and other objects and features of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings which form a part of this specication, and in which:

FlGURE l is a partially broken-away cross-sectional View of the basic particle separating means of the invention comprising a particle-receiving chamber having spaced screens therein together with collecting means for receiving particles passing through the spaced screens;

FiG. 2 is a cross-sectional view taken along line II-ll' of FlG. l illustrating the pinch valve system used in the apparatus of FIG. l;

FIG. 3 is a cross-sectional View taken lli-lll of FIG. l illustrating the vane-type feeding apparatus of the embodiment of FIG.

FIG. 4 is a schematic illustration of the manner in which a plurality of the particle separating devices of FIG. l may be connected in series and operated on an automatic or semi-automatic basis for segregating a batch of particles into a plurality of different size ranges.

Referring now to the drawings, and particularly to along line continuous l; and

' explanation.

FIGS. l-3, there is shown a particle-receiving chamber, generally indicated by the reference numeral it). It comprises a cylindrical vial l2 having a cooperating cylindrical vial insert lle carried on its inner periphery. As shown, the vial l2 and insert lll are each provided with registering elongated slots t6 at their opposite ends. Integral with the vial l2 is a circumferentially extending flange 18 having two radially-extending openings 2U and 22 therein. Preferably, both of the openings Ztl and 22 will be located at the top of the vial l2; however, they are shown at the top and bottom herein for purposes of Surrounding the opposite ends of the vial 12 and covering the elongated openings Il@ are two cylindrical screens 24 and 25 which are carried on pairs of screen frames 26 and 27 and litted over the outer peripheral surface `of the vial l2 between opposite sides of flange 13 and the ends of the vial 12.

it will be noted that the vial insert 14 has an axial length shorter than that of the vial i2 itself, thereby providing annular seats 28 and 29 which receive disc-shaped end plates 3@ and 31. Fitted over the ends of the chamber l@ are cup-shaped housing sections 32 and 33 which have diameters approximating that of the outside diameter of flange Il. The edges of the sections 32 and 33 are provided with annular seats 34, the arrangement being such that the two sections may be held against the ange i8 by clamps or arms, not shown, which are drawn together to hold the housing sections 32 and 33 in abutting relationship with the flange. When the sections 32 and 33 are thus clamped in position, they will also hold the end caps 3b and 3l in position against the op'p` site ends of the vial insert 14/ while/forming air manifolds A and B at the oppositeed's of the vial.

Egtending'through the walls of the housing sections 32 and 33 to manifolds A and B are two inlet ports 36 and 37 as well as two outlet ports 33 and 39. Inlet ports 36 and 37 are connected through flexible plastic tubes It@ and 41, respectively, and a throttle valve pressure regulator 42 to a source of fluid under pressure, generally indicated at 44. Between the valve 42 and the inlet ports 35 and 37 is a pulsing mechanism 45, hereinafter described in detail, which serves to alternately admit tiuid under pressure into tubes 4@ and di. In a similar manner, the outlet ports 38 and 39 are connected through flexible plastic tubes 46 and 47, respectively, and the pulsing mechanism 44 to the inlet ports 48 and 49 of a filtering or settling chamber t).

As shown in FIG. 3, the pulsing mechanism 45, in its simplest form, comprises a block having a generally rectangular cavity 52 formed therein and adapted to receive a cover plate 54 (FIG. l). Reciprocable within the cavity 52 is a bar 56 which is connected through rod 58 to an air cylinder, schematically illustrated at et). Formed through the screen 24 into manifold A and tube 46 where they are conducted to the settling chamber 50. On the next cycle of air cylinder 60, then, the bar 56 moves upwardly, thereby pinching tubes 41 and 46 and closing them off while permitting air from source 44 to flow through throttling valve 42 and tube 4t) int-o the annular manifold A formed by housing section 32 at the left end of chamber 1t). Gn this half of the cycle, the particles which were previously blasted against the screen 24 are forced back into the chamber l@ while the particles of a size to pass through screen flow through this screen which was previously cleaned on the preceding pulse and into manifold B and tube 47 where they are conducted to the settling chamber 50.

As will be understood, the air in tubes 40 and 41 is pulsed at a very high rate of speed to constantly reverse the air flow through chamber 10 during a particle separating operation to clean one of the screens 24 or 25 while simultaneously blasting particles against the other screen. Due to the high speed of operation, particles of a size to pass through either one of the screens 24 or 25 are removed from chamber 10 very rapidly also, the result in the cover plate 54 and the bottom of cavity 52 are Y axially aligned holes lthrough which pass the flexible tubes eti, il and 46, 47. It will be noted that the tubes 4l. and 46 are on one side of the reciprocating bar 56; whereas the tubes 4@ and 47 are on the other side of the bar. The air cylinder 64B is connected through valving, schematically illustrated at 62, to a source of fluid under pressure 64 which may be the same source as source 44 shown in FIG. l, if desired. The valving mechanism 62 is such as to cause the air cylinder 6) to reciprocate its piston, not shown, back and forth at high speed, thereby reciprocating the bar 56 also. downwardly as shown in FG. 2, it will pinch and close off tubes and 47. Under these circumstances, fluid under pressure will flow from source 44 through reducing valve f 42 and through tube 41 to the air manifold B fo-rgrhed between housing section 33 and lthe right end of vial 14. From manifold B, the air flows through screen 25 and into the chamber 10 through openings 16, thereby cleaning the screen 25. In this process, the air is forced out of charnber l@ through screen 24 at the opposite end of the chamber, and this air carries with it particles which pass As the bar 56 movesV being that particles removed from the chamber will be of a size to pass through the screens 24 and 25.

The settling chamber 50, in this case, comprises a funnel-shaped housing 65 having a threaded insert 68 fitted (i,

into its lower end. The insert 68, in turnkreeeives/t glass bottle 70 or any other,suitablerceptacle for'receiving particlesaftertiiey have passed into chamber 50. The upper edge of housing 66 is provided with an annular seat -which receives a gasket 72. Positioned on the gasket 72 is a removable disc 74 of filter paper or the like which serves to permit the air under pressure to pass therethrough while retaining the ground material within chamber 50 in order that it may `fall into the receptacle 7). The chamber 50 is closed by means of a circular cover 76 provided with an annular flange 78 which carries, at its bottom surface, a screen 80, the purpose of the screen being to give support to the lter paper 74. Provided in the cover 76 -is an opening S2 which may, if desired, communicate directly with the atmosphere or with a valve S4 which is normally open to permit the fluid under pressure to pass `to the atmosphere through conduit 86. The cover 76 is secured to the housing 66, as shown, by means of a plurality of wing nuts S8.

Although the cup-shaped housings 32 and 33 may be removed from ythe chamber yit) and the particles to be segregated inserted therein, they may also be `fed into the chamber by apparatus including a storage bin 9b having a removable upper cap 92. The lower end of storage bin 19d is funnel-shaped as shown and communicates with an opening 94 in block 96. Intersecting the opening 9d in block '96 is a bore 98 which receives a vane-type feeder litt), possibly best shown in IFIG. 3, which is rotata- `bly driven through shaft MP2 by means 4of an electric motor dbd or other suitable source of motive power. As shown, the motor 1M is provided with a motor control circuit |166 and a pushbutton switch i108, the arrangement being such that the .pushbutton dii may be selectively depressed to rotate motor 164. Between the Ifeeder lttti and an end plate llt) is a cylindrical spacer 1&2. With the arrangement shown, the material to `be segregated in bin gti will be conveyed by feeder N0 to a exible plastic or other similar tube 1114 which leads to a threaded fitting lM7, this latter :fitting being screwed yinto -opening 2t? provided in annular ange 't8 as was previously explained. Y

yUnder ordinary circumstances, material from bin 9b to be sieved, after being fed into tube 114 by feeder 1th), will not readily fall into the chamber 10 due to the back pressure therein and possibly due to the tendency of the material to cling to thek sides of the tube zille. Accordingly, means are provided for forcing the material to be screened into the chamber 10, and this means comprises a passageway which serves to conduct air under presademas sure into the lower half of opening 94 where it will force the material carried by the feeder into `the chamber 1t). As shown, the passageway 116 is connected through a reducing valve or pressure regulator 1118 to the source of high pressure uid 44, the arrangement being such that the pressure in passageway 11d will be equal to, or slightly greater than, the pressure in tubes 40 and 41 after passing through the throttling valve `42.

- Threaded into opening 22 in the annular flange 1S iS a check valve assembly, generally indicated at 12d, it being understood that the check valve may lbe replaced by other valve means as will hereinafter be explained. The check valve of the particular embodiment of FIG. l includes a valve seat 122 having a check valve member 124 seated thereon by means of a coil spring 126, this coil spring being interposed between the check valve member and the bottom of `a cylindrical chamber 123 which contains the check valve member. Drilled into the bottom of the aforesaid cylindrical chamber v12Svare a plurality of circumferentially spaced holes 130 which permit iluid under pressure and particles within chamber 1t? to pass to a 'fitting 1132 which may, for example, be connected to a tube Iwhich leads to a particle-receiving bin.

As was explained above, the opening 122 which receives the check valve assembly 120 will usually be at the top of chamber 1t) to prevent particles from collecting above valve member 124 during the separating process when air is pulsed into the chamber through tubes 4@ and 41; it being understood .that it is shown at the bottom of the chamber herein ifor purposes of illustration only.

`Connected in parallel with the pressure regulator 42 leading to ports `36 and 37 is a second valve 14d which is controlled by means of an electrical solenoid 142. Valve 140 is normally closed but may be opened by energizing the solenoid i142. Connected in series with solenoid 142 is a second solenoid 144 which, lwhen energized, is adapted to close the normally open valve 84 associated with the settling chamber 50, assuming that this latter valve is employed. Obviously, if valve 84 `is eliminated, the solenoid I144 may be eliminated also. Both of the Solenoids 142 and '144 are controlled by means of a pushbutton switch 146, substantially as shown.

In the operation of the device, the pushbutton 1% will be initially depressed to rotate the motor 104 whereby particles to be segregated will be fed from storage -bin 90 into the chamber 10. At the same time, the pulsing mechanism 62 will cause cylinder 60 to oscillate the bar 56 back and forth to alternately open and then close the inlet and outlet tubes 44, 41 and 4d, 47 communieating 'with the chamber 10. The pressure of source 44 may, for example, ybe about one hundred pounds per square inch. The valves 42 and 11S, however, Iwill reduce this pressure to about ten pounds per square inch so that air is alternately pulsed into the chamber 1@ through one and then the other of the screens 24 and 25 at about ten pounds per square inch also. In this process, particles ofa size to pass through screens 24 and 25 will be collected in settling chamber 5t?, while particles above this size will be retained within the chamber 1i). The spring 125 in check valve assembly 125.1 is such that the valve will not open under a pressure of ten pounds per square inch for the `example given when particles are being separated in the chamber 111.

To clean the chamber 1@ of particles of a size too large to pass through the screens 24 and 25, the pushbutton switch 146 is depressed, thereby energizing Solenoids 142 and 144. When solenoid 144 is energized, it closes valve 84, thereby closing off the chamber 1@ from the atmosphere. At the same time, when solenoid 142 is energized, it will open valve 140 to admit fluid under high pressure (i.e., one-hundred pounds per square inch for the example given) into tube 40 and/or tube 41 where it enters the chamber 10. The high pressure directly from source 44, unlike that through throttle valves 42 and 118, will be sufficient to open the check valve 124.

Thus, theV check valve will open and particles of a size 'too large to pass through screens 24 and 25 will be blown out of chamber 1t) and through holes 131i into the tting 132 where they may be passed to a receiving bin. After all particles have been blown out of the chamber 11i, the pushbutton 146 will be released to deenergize the Solenoids 142 and 144, thereby opening valve 84 and closing valve 140. To start a new cycle of operation, the pushbutton switch 10S will be depressed to rotate the motor 14 and feed a new batch of particles to be separated into'the chamber 10 where the foregoing process is repeated.

Alternatively, the particles of a size too large to pass through screens 24 and 25 may be blown out of chamber 10 by the arrangement shown in dotted outline in FIG. 1. With this arrangement, the valve will be replaced by a normally closed valve 140 connected in shunt with the throttle valve 11S. Valve 140 may be opened by means of a solenoid 142. which is substituted for solenoid 142 and connected in series with pushbutton switch 146 and solenoid 144. Thus, when pushbutton switch 146 is now depressed, valve 14d will open and valve 84 will close, but pressure of one-hundred pounds per square inch directly from source 44 will now be forced into chamber 10 through passageway 116V rather than through tubes 40 and 41, .the result being the same (i.e., to blow the larger particles out through check valve assembly 120).

Referring now to FIG. 4, three particle separating chambers identified by the numerals 10a, 10b and 10c are shown connected in series with the output from chamber 10a being fed to the input of chamber 10b, and so on. Elements in FIG. 4 which correspond to those OfFIGS. l-3 are identified by like reference numerals, except that those elements associated with chamber lila have the letter a after each numeral, those associated with chamber 10b have the letter b associated with each numeral, and those associated with chamber 10c have the letter c after each numeral.

Unlike the embodiment of FIG. l wherein a check valve is employed at the output of chamber 14B, chamber 10a of FIG. 4 is connected through a normally closed solenoid-operated valve 150 and conduit 152 to the inlet of chamber 10b. Likewise, the outlet of chamber 19h is connected through normally closed solenoid-operated valve 154 and conduit 156 to the inlet of chamber 10c; and the outlet of chamber 10c is connected through normally closed solenoid-operated valve 158 to conduit 160 which may, if desired, be connected to the inlet of a succeeding particle-receiving chamber.

High pressure source 44 is connected through conduit 159 and throttle valves or pressure regulators 42a, 42h and 42C to the inlet tubes 4941-490 and 41o-41C of the respective chambers 10a-13C. Connected in shunt with pressure regulators 42a-42c are normally closed solenoid-operated valves 162, 154 and 166, respectively. Solenoids 16S and 170 for valves 150 and 162 are connected in series with pushbutton switch 146o; Solenoids 172 and 174 for valves 154 and 164 are connected in series with pushbutton switch 14b; and Solenoids 176 and 178 for valves 15S and 166 are connected in series with pushbutton switch 146e. It will be noted that in this particular embodiment, no valves are provided at the out puts of collecting chambers Stia-59C, however they may be Vprovided if found to be desirable. ln 4this later case, the Solenoids for the valves on chambers Stia-Stic would be connected in series with the other Solenoids for the respective chambers, the arrangement being such that the valve for chamber 59a, for example, would close when valves 150 and 162 open. As will be understood, the spaced screens 24a and 25a of Chamber 10a (not shown in FIG. 4) will be of a smaller mesh size than those of chamber 10b, while the screens of chamber 11th will be of a smaller mesh size than those in chamber 10c.

ln order to effect segregation of the particles in bin 90 into various size ranges, the pushbutton 1G55 will be i? depressed to feed particles into chamber a. These particles within the chamber 10a, under the inuence of the pulsed -air from tubes 40a and 4ta, will pass particles of a size to pass through the screens in this chamber to the collecting chamber 50a. After this particle-separating step is achieved, pushbutton switch 14661 will be depressed to open valves 150 and 162, thereby admitting fluid under high pressure from source 44 into chamber 10a. This forces particles within chamber toa above the size range of the Screens in chamber 10a to pass through valve 150, which is now open, into chamber i011. Thereafter, the pushbutton switch 146er is released and pushbutton switch 108 will again be depressed to feed more particles to be segregated into chamber 10a. Under these circumstances, particle segregation will occur in both of the chambers 10a and 10b with the particles from chamber 10b passing to collecting chamber 50b being larger than those passing to collecting chamber Stia since, it will be remembered, the screens of chamber 10b are of a larger mesh size than those of chamber 10a. After a predetermined amount of time has elapsed sufficient to permit all particles of a size to pass through the screens in chambers lilla and lttb to he collected-in Vchambers SaanrLStb, the pushbutton switch 146]? will rst be'ieressei thereby opening valves 154 and 164 and pressed to feed another batch of particles from bin 90 into chamber 10a. All of the chambers Mia, 10b and 10c are now effecting particle segregation, with those particles passing to the collec/ting chamber (50c being larger than those passing/to the collecting chamber 50b, and those passing to collecting chamber 50a being smaller than those passing to chamber 5017.

After all particles of a size to pass through the screens in chambers 16a, 10b and 16e have been collected in their associated chambers Stia-Stic, the pushbutton switch 146e will rst be depressed to open valves 158 and 166 and thereby admit fluid under high pressure into the chamber 10c. This forces the particles remaining in chamber Mic out through the valve 158 to conduit 160 which may, for example, be connected to a succeeding particle separating chamber. Following the closure of pushbutton switch 146C, pushbutton switch 14615 Ywill be closed, followed by closure of pushbutton switch 146a. it can thus be seen that in this manner the larger particles are progressively passed from chamber llta to chamber liltb to'chamber 10c, with each chamber removing particles through its spaced screens which are progressively larger in size.

Athough the invention has been shown in connection with a certain specific embodiment, it will be readily apparent to those skilled in the art that various changes in form and arrangement of parts may be made to suit requirements without departing from the spirit and scope 4of the invention. In this respect, it will be apparent that the alternative valving arrangement of FIG. 1 may be employed in the system of FIG. 4 and that the successive Aclosure of pushbutton switches tlt, M661, llib and 146C in FIG. 4 may be effected automatically by apparatus well known to those skilled in the art.

I claim as my invention:

1. Particle separating means comprising a closed particle-receiving chamber, first means for conveying particles into said chamber, second means for conveying particles out of the chamber, check valve means in the second means adapted to open in response to a pressure above a predetermined pressure in the chamber to discharge partiCleS therefrom, spaced openings in the chamber walls, particle separating means covering said openings in the chamber walls and adapted to pass particles of a predetermined size, means for alternately causing uid to flow into said chamber through one and then the other of said particle separating means at a pressure below said predetermined pressure to alternatively carry particles in the chamber to one and then the other of said particle separating means, collecting means for receiving material passing through the particle separating means, and means for forcing fluid at a pressure above said predetermined pressure into the chamber after particles of a size to pass through the particle separating means have passed to the collecting means whereby particles larger than said predetermined size will be blown out of the chamber through said check valve means.

2. Particle separating means comprising a closed particle-receiving chamber, first conduit means for conveying particles into said chamber, second conduit means for conveying particles out of the chamber, normally closed valve means in the second conduit means, spaced openings in the chamber walls, screens covering said openings in the chamber wall'sand adapted to pass particles Yof a predetermined size,.means for alternately causing fluid to ow into said chamber through one and then the other of said screens to alternately carry particles in the chamber to one and then the other of said screens, collecting means for receiving material passing through the screens, and single means for opening said valve means and for forcing fluid under pressure into the chamber after particles of a size to pass through the screens have passed to the collecting means whereby particles larger than said predetermined size will be blown out of the chamber through said valve means.

3. Particle sepa/rating means comprising a closed particle-receiving'hamber, first conduit means for conveyingparticles into said chamber, second conduit means for conveying particles out of the chamber, check valve means in the second conduit means adapted to open in response to a pressure above a predetermined pressure in the chamber to discharge particles therefrom, spaced openings in the chamber walls, particle separating means covering said openings in the chamber walls, a pair of manifolds disposed over said particle separating means and said openings, means for alternately creating a pressure in one of said manifolds which is higher than that in the other manifold to alternately cause particlesY in the chamber lto move against one Yand .thentheother of said particle separating means, (the pressure created in said manifolds being below said predetermined pressure, collecting means receiving material passing through said particle separating means, and means for forcing fluid at a pressure above said predetermined pressure into the chamber after particles of a size to pass through the particle separating means have passed to the collecting means whereby particles larger than said predetermined size will be blown out of the chamber through said check valve means;

4. Particle separating means comprising a closed particle-receiving chamber, first conduit means for conveying particles into said chamber, second conduit means for conveying particles out of the chamber, normally closed valve means in the second conduit means, spaced openings in the chamber walls, screen means covering said openings in the chamber walls, a pair of manifolds disposed over said screen means and said openings, uid inlet and outlet means for each of said manifolds, means acting on said inlet and outlet means to alternately open the inlet means and close the outlet means at one manifold while simultaneously opening the outlet means and closing the inlet means at the other manifold whereby fluid may be pulsed in alternate directions through the screen means and chamber to alternately carry particles against one and then the other of said screens, collecting 4means for receiving material passing through the screen (means, and single means for opening said valve means aisance and for forcing fluid under pressure into the chamber after particles of a size to pass through the screen means have passed to the collecting means whereby particles larger than said predetermined size will be blown out of the chamber through said valve means.

5. Particle separating means comprising a closed particle-receiving chamber, normally closed valve means in the chamber adapted to open to discharge particles therefrom, a storage bin for particles to be separated, means for selectively conveying particles from said storage bin to said chamber, spaced openings in the chamber walls, screens covering said openings in the chamber walls and adapted to pass particles of a predetermined size, means for alternately forcing uid at a predetermined pressure into said chamber through one and then the other of said screens to alternately carry particles in said chamber to one and then the other of said screens, collecting means receiving material passing through said screens, means for stopping the delivery of particles from said storage bin to said chamber, and single means operative during stoppages in the delivery of said particles to said chamber for opening said valve means and forcing iluid at a pressure above said predetermined pressure into the chamber after particles of a size to pass through the screens have passed to the collecting means whereby particles larger than said predetermined size will be blown out of the chamber through said valve means.

6. Particle separating means comprising a plurality of closed particle-receiving chambers, conduit means connecting said particle-receiving chambers in series whereby particles may pass through the serially-connected chambers in succession, normally closed valve means in the conduit means adapted to open to permit particles to pass through successive ones of said chambers, spaced opening in the chamber walls, particle separating means covering said opening and adapted to pass particles of a predetermined size, means for alternately causing uid to ow into each chamber through said particle separating means to alternately carry particles in the chamber to one and then the other of said particle separating means, a plurality of collecting devices each of which receives material passing through the particle separating means of an associated one of said chambers, and means for opening said valve means and for forcing fluid under pressure into each chamber after particles of a size to pass through the particle separating means in that chamber have passed to the collecting device for the chamber, the arrangement being such that the latter-mentioned iiuid under pressure will force particles which have not passed through the particle separating means of each chamber out of that chamber and into the next successive chamber.

7. Particle separating means comprising a closed particle-receiving chamber, first means for conveying particles into said chamber, second means for conveying particles out of the chamber, normally closed valve means in the second means, spaced openings in the chamber walls, screens covering said openings in the chamber Walls and adapted to pass particles of a predetermined size, a first pair of conduits each of which is adapted to convey uid at a predetermined pressure into said chamber through an associated one of said screens, a second pair of conduits each of which is adapted to carry particles out of said chamber which pass through an associated one of said screens, unitary valve means for alternately opening and then closing one conduit in sai-d first pair associated with one of said screens while reversely closing and then opening the other conduit in said first pair associated with the other of said screens and for simultaneously alternately opening then closing the conduit in said second pair associated with said other of said screens while reversely closing then opening the other conduit in said 4second pair whereby fluid is pulsed in alternate directions through the screen and chamber to alternately carry particles against one and then the other of said screens, and single means for opening said normally closed valve means and for forcing fluid at a pressure above said predetermined pressure into the chamber after particles of a size to pass through the screens have passed to the collecting means whereby particles larger than said predetermined size will be blown out of the chamber through said valve means.

References Cited in the file of this patent UNITED STATES PATENTS 339,723 Winkler Apr. 13, 1886 488,067 Foster Dec. 13, 1892 1,497,792 Perkins June 17, 1924 1,528,983 Montgomery Mar. 10, 1925 1,530,193 Montgomery Mar. 17, 1925 2,058,959 Denning Oct. 27, 1936 2,996,183 Russum Aug. 15, 1961 FOREIGN PATENTS 344,227 Great Britain Mar. 5, 1931 

1. PARTICLE SEPARATING MEANS COMPRISING A CLOSED PARTICLE-RECEIVING CHAMBER, FIRST MEANS FOR CONVEYING PARTICLES INTO SAID CHAMBER, SECOND MEANS FOR CONVEYING PARTICLES OUR OF THE CHAMBER, CHECK VALVE MEANS IN THE SECOND MEANS ADAPTED TO OPEN IN REPONSE TO A PRESSURE ABOVE A PREDETERMINED PRESSURE IN THE CHAMBER TO DISCHARGE PARTICLES THEREFROM, SPACED OPENINGS IN THE CHAMBER WALLS, PARTICLE SEPARATING MEANS COVERING SAID OPENINGS IN THE CHAMBER WALLS AND ADAPTED TO PASS PARTICLES OF A PREDETERMINED SIZE, MEANS FOR ALTERNATEDLY CAUSING FLUID TO FLOW INTO SAID CHAMBER THROUGH ONE AND THEN THE OTHER OF SAID PARTICLE SEPARATING MEANS AT A PRESSURE BELOW SAID PREDETERMINED PRESSURE TO ALTERNATIVELY CARRY PARTICLES IN THE CHAMBER OT ONE AND THEN THE OTHER OF SAID PARTICLE SEPARATING MEANS, COLLECTING MEANS FOR RECEIVEING MATERIAL PASSING THROUGH THE PARTICLE SEPARATING MEANS, AND MEANS FOR FORCING FLUID AT A PRESSURE ABOVE SAID PREDETERMINED PRESSURE INT THE CHAMBER AFTER PARTICLES OF A SIZE TO PASS THROUGH THE PARTICLE SEPARATING MEANS HAVE PASSED TO THE COLLECTING MEANS WHEREBY PARTICLES LARGER THAN SAID PREDETERMINED SIZE WILL BE BLOWN OUT OF THE CHAMBER THROUGH SAID CHECK VALVE MEANS. 